Electric discharge device



Aug. 7, 1934- G. M. BEARDOW 1,969,496

ELECTRIC DISCHARGE DEVICE Filed March 12, 1931 FIG. I

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- INVENTOR QMBEARDOW A T TORNE) Patented Aug. 7, 1934 I I UNITED. STATES PATENT OFFICE ELECTRIC DISCHARGE DEVICE George M. Beardow, White Plains, N. Y., alsignor to Bell Telephone Laboratories, Incorgorraktetl, New York, N. Y., a corporation of New Application March 12, 1931, Serial No. 521,958 8 Claims. (Cl. 250-215) This invention relates to electric discharge decuit. A plurality or rigid wires 15, each of which vices and more particularly to gaseous rectiflers is electrically connected to one at the terminal employing an incandescent cathode. prongs 14, are embedded in the press 12 and An object of this invention is to increase the support a helical cathodelfi through flexible meefliciency of electric discharge devices. tallic link members 17, welded to the wires 15 60 Another object of this invention is to simplify and to opposite ends of the cathode 16. The and improve the structure of discharge devices. link members allow longitudinal expansion and The discharge device of this invention comcontraction of the cathode with temperature prises, in one embodiment, an evacuated vessel variations. The cathode consists of a flat nickel 0 having a reentrant stem, a cathode supported ribbon coated with alkaline earth oxides, for ex- 5 from the stem and extending longitudinally of ample, barium and strontium oxides and is the vessel, and an anode disposed adjacent the formed into a cylindrical spiral or helix having end of the cathode remote from the stem. The closely spaced fiat-wound turns, the axis of the cathode consists of a helical ribbon adapted to spiral or helix being coincident with the longi- 15 emit electrons when heated and is supported by tudinal axis of the vessel 10. 70 two upright metallic rods embedded in the stem. Due to the length of the cathode and its sus- The ends of the helical cathode are connected to pension it is susceptible to external shock and the upright rods by flexible links welded thereto. subject to lateral displacement by temperature In accordance with one feature of this invenvariations during operation. of the device. To

tion the rigidity of the cathode structure is inovercome vibration and displacement of the 75 creased by an auxiliary supporting rod embedded cathode a rigid metallic rod 18 is embedded in in the press and extending axially within the the press 12 and extends centrally within the helicathode. The auxiliary rod carries two spaced cal cathode 16 along the axis thereof and pararms which engage the cathode and prevent exallel to the supporting rods 15. A pair of U- cessive jarring thereof by external shock and also shaped arms 19, of a material having a high prevent distortion of the cathode by temperature resistivity, such as molybdenum, are spaced along variations. the rod 18 and are welded thereto at right angles In accordance with another feature of this into h other. The Vertical p s 0f the arms 19 vention, a cylindrical metallic shield of relatively engage the helical Cathode 16 ihtelierly thereof 30 low heat conductivity Surrounds t cathode at approximately the central portion of the helix. 5 throughout t entire length The Shield The coating on the cathode serves to some extent serves and confines t heat radiated by the m. as an insulating medium between the arms 19 and ode and thereby increases t thermal em iency the cathode 16 so that the convolutions of the of the cathode and the overall emeieney of the cathode are not shorted electrically by the arms discharge device 19. Furthermore, the arms 19 being of a material These and other features or this invention will having a high resistivity, the current therebe more clearly understood from the following through comparlem t0 the Cathode heati g detailed description with reference to the accomcurrent W111 heeessarlly be Smallpanying drawing i hi h; This construction provides a compact and rigid 40 Fig. 1 is a perspective view of a mercury vapor athod h vi a relatively large electron emitrectifier made in accordance with this invention tine u a a d having a figur s a t portions f th th d a d of th h at, a concentrated field of electronic flow is provided shield broken away to show the cathode structure in the direction of the axis of the c9Jihodemore clearly; thermore, since the convolutions of the cathode 45 Fig. 2 is an enlarged detail view in elevation of a e clo ly sp ce a substantially closed yl the cathode structure; and drical structure is formed which increases the Fig. 3 is a plan view or the cathode str cture transfer or heat between the turns of the helix, shown in Fig. 2. decreases radiation of heat from the cathode and Referring now to the drawing, the electric disth r y im v t r al fi i y f th charge i i orda e with o e mb dicathode and the overall efliciency of the discharge ment or this invention, comprises an enclosing device. vessel 10 having a reentrant stem 11 terminating In order to further conserve the heat of the in a press 12. The vessel 10 is attached to an cathode and thereby reduce the current necesinsulating base 13 carrying terminal prongs 14 sary to heat the cathode to a temperature retor associating the device with an electrical cirquired for satisfactory electron emission, a shield 1 20 of a material of relatively low heat conductivity, such as nickel, is disposed about the cathode 16 throughout its entire length. The shield 20 is preferably cylindrical in form and is closely spaced about the helical cathode and provided with a pair of integral flanges 21which surround and engage one of the cathode supporting rods 15.

- The cylindrical shield serves as a heat reflector to confine and concentrate the cathode heat to a restricted space immediately about the cathode and minimizes heat radiation from the cathode to the wall of the enclosing vessel 10.

A leading-in wire 22 is sealed in the end of the vessel 10 opposite the stem 11 and is connected to a metallic cap 23 attached to the vessel 10 and serving as an external terminal for the anode'of the discharge device. A dished anode 24, preferably of carbonized molybdenum, is supported from the leading-in wire 22 and is disposed with its base substantially perpendicular to the longitudinal axis of the cathode 16.

A helmet-shaped metallic disc 25 carrying a pellet of a getter material, such as magnesium, for fixing residual gases in the device, is supported from one of the rods 15 by a bent wire or shank 26 welded thereto.

In the assembly of the device, the vessel 10 is evacuated to a high degree and a quantity of mercury 2'7 is injected into the vessel 10 through a tubulation 28 within the stem 11 in accordance with the method disclosed in a copending application of D. S. Bond, Serial No. 480,654,.filed September 9, 1930. During the operation of the device, the mercury is vaporized to form the conducting medium between the cathode and anode of the rectifier.

Although a specific embodiment of the invention has been disclosed and described herein, it is to be understood that the invention is not limited thereto and that many modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. In an electric discharge device having a stem, a hollow filamentary electrode supported above said stem, a support mounted on said stem and extending within said electrode, and a plurality of members mounted on said support, the outer portions of said members slidably engaging the inner surface of middle portions of said electrode for preventing lateral displacement thereof.

2. In an electric discharge device, an electrode structure comprising a stem, a plurality of parallel rigid members supported from said stem, a helical electrode mounted on said members, parallel rigid members supported from said stem, and extending within said helical electrode, and a helical electrode mounted on said members, engaging said electrode interiorly thereof.

3. In an electric discharge device, an electrode structure comprising a stem, a plurality of parallel rigid rods supported from said stem, a helical electrode mounted on said rods, a rigid member supported from said stem and extending within said electrode, and a metallic member having a high electrical resistance relative to said electrode mounted on\said rigid member and engaging said electrode interiorly thereof.

4. In an electric discharge device, an electrode structure comprising a stem, a plurality of parallel rigid rods supported from said stem, a helical electrode mounted on said rods, a rigid member supported from said stem and extending within said electrode, and a plurality of U-shaped arms on said rigid member disposed at an angle to one another and engaging said helical electrode interiorly thereof.

5. A mercury vapor discharge device comprising an enclosing vessel having a stem, a plurality of rods extending from said stem, a helical cathode mounted on said rods and having its axis coincident with the axis of said stem, a rigid member supported from said stem and extending within said cathode, means on said member engaging said cathode interiorly thereof, a cylindrical shield mounted on one of said rods and encircling said cathode throughout its entire length, and an anode disposed adjacent an end of said cathode and substantially perpendicular to the axis thereof.

- 6. An electric discharge device comprising an enclosing vessel having a stem, a plurality of rods extending'above said stem, a cathode supported by said rods, consisting of a fiat ribbon forming a cylindrical spiral, a rigid member embedded in said press and extending axially within said spiral, and means on said rigid member engaging said spiral interiorly thereof.

7. An electric discharge device comprising an enclosing vessel having a stem, a pair of rigid rods extending above said stem, a cathode comprising a flat ribbon forming a linear helix having closely spaced convolutions, said rods serving as leading-in conductors for said cathode, link members between the ends of said helix and said rods, a heat reflecting member mounted on one of said rods and encircling said cathode, and an anode supported from the opposite end of said vessel substantially at right angles to the axis of said cathode.

8. An electric discharge device comprising an anode and a cylindrical helically wound cathode, means for supporting the cathode at its longitudinal ends and additional supporting means within said cathode and intermediate the ends thereof contacting with a plurality of turns of said cathode at a plurality of points on said turns. 

